Reflective eyepiece optical system and head-mounted near-to-eye display device

ABSTRACT

The present invention relates to a reflective eyepiece optical system and a head-mounted near-to-eye display device. The system includes: a first optical element and a second optical element which are arranged sequentially along an incident direction of an optical axis of human eyes, and a first lens group located on an optical axis of a miniature image displayer; wherein the first optical element and the second optical element are used for transmitting and reflecting an image light from the miniature image displayer; the first optical element reflects the image light passing through the first lens group to the second optical element, and then transmits the image light reflected by the second optical element to the human eyes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to Chinese patent application No. 202110879682.8, filed on Aug. 2, 2021, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the field of optical technology, and more particularly, to a reflective eyepiece optical system and a head-mounted near-to-eye display device.

BACKGROUND

With the development of electronic devices to ultra-miniaturization, head-mounted display devices and products are constantly emerging in military, industrial, medical, educational, consumption and other fields, and in a typical wearable computing architecture, a head-mounted display device is a key component. The head-mounted display device directs the video image light emitted from a miniature image displayer (e.g., a transmissive or reflective liquid crystal displayer, an organic electroluminescent element, or a DMD element) to the pupil of the user by optical technology to implement virtual magnified images in the near-eye range of the user, so as to provide the user with intuitive, visual images, video, text information. The eyepiece optical system is the core of the head-mounted display device, which realizes the function of displaying a miniature image in front of human eyes to form a virtual magnified image.

The head-mounted display device develops in the direction of compact size, light weight, convenient wearing, and load reduction. Meanwhile, a large field-of-view angle and visual comfort experience have gradually become key factors to evaluate the quality of the head-mounted display device. The large field-of-view angle determines a visual experience effect of high liveness, and high image quality and low distortion determine the comfort of visual experience. To meet these requirements, the optical system should try its best to achieve such indexes as a large field-of-view angle, high image resolution, low distortion, small field curvature, and a small volume. It is a great challenge for system design and aberration optimization to satisfy the above optical properties at the same time.

In Patent Document 1 (Chinese Patent Publication No. CN101915992A), Patent Document 2 (Chinese Patent Publication No. CN211698430U), Patent Document 3 (Chinese Patent Publication No. CN106662678A), and Patent Document 4 (Chinese Patent Publication No. CN105229514A), a reflective optical system utilizing a combination of traditional optical spherical surfaces and even-order aspherical face shapes is provided respectively, wherein Patent Document 1 adopts a relay scheme, but this scheme adopts a free-form surface reflection means, which greatly increases the difficulty of realizing the entire optical system; the optical systems in the Patent Document 2, Patent Document 3 and Patent Document 4 use reflective optical systems, but the basic optical structures vary greatly from one to another due to different application fields, such as in terms of a matching relationship between a lens face shape and a gap between the lenses.

Patent Document 5 (Chinese Patent Publication No. CN207081891U) and Patent Document 6 (Chinese Patent Publication No. CN108604007A) provide an eyepiece optical system that adopts a reflex means, which ensures high-quality imaging; however its optical structure is often limited to single lens reflection, thereby greatly limiting a performance ratio of the entire optical structure.

To sum up, the existing optical structures not only have problems such as heavy weight, small field-of-view angle, and insufficient optical performance, but also have problems such as difficulty in processing and mass production due to the difficulty of implementation.

SUMMARY

The technical problem to be solved by the present invention is that the existing optical structure has the problems of heavy weight, low image quality, distortion, insufficient field-of-view angle, and difficulty in mass production. Aiming at the aforementioned defects of the prior art, a reflective eyepiece optical system and a head-mounted near-to-eye display device are provided.

The technical solutions adopted in the present invention to solve the technical problem thereof are as follows: constructing a reflective eyepiece optical system, including: a first optical element and a second optical element arranged sequentially along an incident direction of an optical axis of human eyes, and a first lens group located on an optical axis of a miniature image displayer; the first optical element is used for transmitting and reflecting an image light from the miniature image displayer; the second optical element includes an optical reflection surface, and the optical reflection surface is concave to a human eye viewing direction; the first optical element reflects the image light refracted by the first lens group to the second optical element, and then transmits the image light reflected by the second optical element to the human eyes;

an effective focal length of the eyepiece optical system is f_(w), an effective focal length of the first lens group is f₁, an effective focal length of the second optical element is f₂, and f_(w), f₁, and f₂ satisfy the following relations (1) and (2): f ₁ /f _(w)<−0.50  (1); f ₂ /f _(w)<−0.70  (2);

the first lens group includes a first sub-lens group and a second sub-lens group arranged sequentially along an optical axis direction from a human eye viewing side to a miniature image displayer side; an effective focal length of the first sub-lens group is f11, which is a positive value; an effective focal length of the second sub-lens group is f12, which is a positive value; and f11, f12 and f1 satisfy the following relations (3) and (4): 0.66<f ₁₁ /f ₁  (3); 0.57<f ₁₂ /f ₁  (4);

the first sub-lens group is composed of two lenses which are a first lens away from the miniature image displayer side and a second lens close to the miniature image displayer side respectively; the first lens is a negative lens; and the second lens is a positive lens.

Further, the distance along the optical axis between the first optical element and the second optical element is d₁, the distance along the optical axis between the first optical element and the first lens group is d₂, and d₁ and d₂ satisfy the following relation (5): 0.69<d ₂ /d ₁  (5).

Further, a maximum effective optical caliber of the second optical element is φ₂, which satisfies the following relation (6): φ₂<70 mm  (6).

Further, an effective focal length of the first lens is f₁₁₁, the effective focal length of the first sub-lens group is f₁₁, and f₁₁₁ and f₁₁ satisfy the following relation (7): f ₁₁₁ /f ₁₁<−0.96  (7).

Further, the effective focal length f₁ of the first lens group, the effective focal length f₁₁ of the first sub-lens group, the effective focal length f₁₂ of the second sub-lens group and the effective focal length f₁₁₁ of the first lens further satisfy the following relations (8), (9) and (10): 0.67≤f ₁₁ /f ₁≤1.42  (8); −2.64≤f ₁₁₁ /f ₁₁≤<0.97  (9); 0.58≤f ₁₂ /f ₁≤4.54  (10).

Further, an included angle of the optical axis between the first lens group and the second optical element is λ₁, which satisfies the following relation (11): 55°<λ₁<120°  (11).

Further, the second sub-lens group is composed of a third lens located between the second lens and the miniature image displayer; the third lens is a positive lens, and an optical surface of the third lens close to the miniature image displayer side is concave to the miniature image displayer;

an effective focal length of the third lens is f₁₂₁, which satisfies the following relation (12): 5.83<f ₁₂₁  (12).

Further, the first optical element is a planar transflective optical element, and a reflectivity of the first optical element is Re₁, which satisfies the following relation (13): 20%<Re ₁<80%  (13).

Further, an optical surface of the second optical element close to the human eye viewing side is a high-reflectivity optical surface, and a reflectivity of the high-reflectivity optical surface is Re₂, which satisfies the following relation (14): 20%<Re ₂  (14).

Further, the eyepiece optical system further includes a planar reflective optical element located between the first lens group and the first optical element; the planar reflective optical element reflects the image light refracted by the first lens group to the first optical element, and the first optical element reflects the image light to the second optical element, and then transmits the image light reflected by the second optical element to the human eyes;

an included angle between the first lens group and the first optical element is λ₂, which satisfies the following relation (16): 60°≤λ₂≤180°  (16).

Further, the second optical element includes two coaxial optical surfaces of the same face shape.

Further, the optical face shape of each lens in the first lens group includes an even-order aspherical face shape; and each optical face shape of the second optical element is the even-order aspherical face shape.

Further, the even-order aspherical face shape satisfies the following relation (15):

$\begin{matrix} {z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{2}r^{2}} + {\alpha_{4}r^{4}} + {\alpha_{6}r^{6}} + {\ldots.}}} & (15) \end{matrix}$

Further, the material of the second optical element is an optical plastic material.

The present application provides a head-mounted near-to-eye display device, including a miniature image displayer, and further including the reflective eyepiece optical system according to any one of the foregoing content; and the eyepiece optical system is located between the human eyes and the miniature image displayer.

Further, the miniature image displayer is an organic electroluminescent device.

Further, the head-mounted near-to-eye display device includes two identical reflective eyepiece optical systems.

The present invention has following beneficial effects: the first optical element has transmission and reflection properties, the second optical element includes a reflection surface, the eyepiece optical system composed of the first lens group, the first optical element and the second optical element is used for effectively folding the optical path, which reduces the overall size of the eyepiece optical system and improves the possibility of subsequent mass production, the first lens group includes a first sub-lens group and a second sub-lens group, and the focal length between each lens adopts a combination of negative, positive, and positive. On the basis of miniaturization, cost and weight reduction for the article, the aberration of the optical system is greatly eliminated, and the basic optical indicators are also improved, ensuring high image quality and increasing the size of the picture angle. Thus an observer can watch large images of full frame, high definition and uniform image quality without any distortion and get visual experience of high liveness via the present invention, which is suitable for near-to-eye displays and similar devices thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the present invention is further illustrated in connection with accompanying drawings and embodiments hereafter. The drawings in the following description are only some embodiments of the present invention. For those of ordinary skills in the art, other drawings may be obtained from these drawings without any creative work.

FIG. 1 is an optical path diagram of a reflective eyepiece optical system according to Example 1 of the present invention;

FIG. 2 is a schematic diagram of a dot array diagram of the reflective eyepiece optical system according to Example 1 of the present invention;

FIG. 3 a is a schematic diagram of a field curvature of the reflective eyepiece optical system according to Example 1 of the present invention;

FIG. 3 b is a schematic diagram of a distortion of the reflective eyepiece optical system according to Example 1 of the present invention;

FIG. 4 is a schematic diagram of an optical transfer function (MTF) of the reflective eyepiece optical system according to Example 1 of the present invention;

FIG. 5 is an optical path diagram of a reflective eyepiece optical system according to Example 2 of the present invention;

FIG. 6 is a schematic diagram of a dot array diagram of the reflective eyepiece optical system according to Example 2 of the present invention;

FIG. 7 a is a schematic diagram of a field curvature of the reflective eyepiece optical system according to Example 2 of the present invention;

FIG. 7 b is a schematic diagram of a distortion of the reflective eyepiece optical system according to Example 2 of the present invention;

FIG. 8 is a schematic diagram of an optical transfer function (MTF) of the reflective eyepiece optical system according to Example 2 of the present invention;

FIG. 9 is an optical path diagram of a reflective eyepiece optical system according to Example 3 of the present invention;

FIG. 10 is a schematic diagram of a dot array diagram of the reflective eyepiece optical system according to Example 3 of the present invention;

FIG. 11 a is a schematic diagram of a field curvature of the reflective eyepiece optical system according to Example 3 of the present invention;

FIG. 11 b is a schematic diagram of a distortion of the reflective eyepiece optical system according to Example 3 of the present invention;

FIG. 12 is a schematic diagram of an optical transfer function MTF of the reflective eyepiece optical system according to Example 3 of the present invention;

FIG. 13 is an optical path diagram of a reflective eyepiece optical system according to Example 4 of the present invention;

FIG. 14 is a schematic diagram of a dot array diagram of the reflective eyepiece optical system according to Example 4 of the present invention;

FIG. 15 a is a schematic diagram of a field curvature of the reflective eyepiece optical system according to Example 4 of the present invention;

FIG. 15 b is a schematic diagram of a distortion of the reflective eyepiece optical system according to Example 4 of the present invention; and

FIG. 16 is a schematic diagram of an optical transfer function MTF of the reflective eyepiece optical system according to Example 4 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, hereafter clear and complete description is made with reference to the technical solutions in the embodiments of the present invention, and the described embodiments are a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skills in the art without any creative work based on the embodiments disclosed in the present invention fall within the claimed scope of the present invention.

In the present invention, a reflective eyepiece optical system is constructed, which includes: a first optical element and a second optical element arranged sequentially along an incident direction of an optical axis of human eyes, and a first lens group located on an optical axis of a miniature image displayer; the first optical element is used for transmitting and reflecting an image light from the miniature image displayer; the second optical element includes an optical reflection surface, and the optical reflection surface is concave to a human eye viewing direction; the first optical element reflects the image light refracted by the first lens group to the second optical element, and then transmits the image light reflected by the second optical element to the human eyes.

The aforementioned light transmission path is as follows: the light generated by the miniature image displayer is refracted by the first lens group and then transmitted onto the first optical element, the reflection part on the first optical element reflects the light onto the second optical element, and the optical reflection surface on the second optical element reflects the received light onto the first optical element. The light-transmitting part on the first optical element will transmit the light to the human eyes.

an effective focal length of the eyepiece optical system is f_(w), an effective focal length of the first lens group is f₁, an effective focal length of the second optical element is f₂, and f_(w), f₁, and f₂ satisfy the following relations (1) and (2): f ₁ /f _(w)<−0.50  (1); f ₂ /f _(w)<−0.70  (2);

wherein the value of f₁/f_(w) may be −0.50, −1.462, −3.398, −11.295, −23.931, −30.891, −44.751, −51.535, −70.479, etc.; and

the value of f₂/f_(w) may be −0.70, −1.93, −3.59, −11.35, −31.12, −45.08, −50.91, −71.88, −80.73, −100.649, etc.

The first lens group includes a first sub-lens group and a second sub-lens group arranged sequentially along an optical axis direction from a human eye viewing side to a miniature image displayer side; the effective focal lengths of the first sub-lens group and the second sub-lens group are a combination of positive and positive; the effective focal length of the first sub-lens group is f₁₁, the effective focal length of the second sub-lens group is f₁₂, and f₁₁, f₁₂ and f₁ satisfy the following relations (3) and (4): 0.66<f ₁₁ /f ₁  (3); 0.57<f ₁₂ /f ₁  (4).

The value of f₁₁/f₁ may be 0.66, 0.77, 0.89, 1.35, 3.25, 5.56, 36.1, 54.1, 87.6, etc., and the value of f₁₂/f₁ may be 0.57, 1.25, 1.33, 1.78, 2.13, 2.55, 3.15, 4.14, 4.53, 4.78, etc.

In the aforementioned relations (1), (2), (3) and (4), the ranges of the values of f₁/f_(w), f₂/f_(w), f₁₁/f₁ and f₁₂/f₁ are closely related to the correction of system aberration, the processing difficulty of the optical elements, and the sensitivity of assembly deviation of the optical elements, wherein the value of f₁/f_(w) in the relation (1) is less than −0.50, which improves the machinability of the optical elements in the system; and the value of f₂/f_(w) in the relation (2) is less than −0.70, so that the system aberration is fully corrected, thereby achieving an optical effect with higher quality. The value of f₁₁/f₁ in the relation (3) is greater than 0.66, so that the system aberration is fully corrected, thereby achieving high-quality optical effect; The value of f13/f1 in the formula (4) is greater than 0.57, so that the system aberration can be fully corrected, thereby achieving a high-quality optical effect.

The first sub-lens group is composed of two lenses which are a first lens away from the miniature image displayer side and a second lens close to the miniature image displayer side respectively; the first lens is a negative lens; and the second lens is a positive lens.

The first lens group includes two sub-lens groups, which are a first sub-lens group and a second sub-lens group arranged adjacently, and the first sub-lens group and the second sub-lens group adopt a focal length combination of positive and positive, wherein in the first lens group, the first lens is a negative lens; the second lens is a positive lens; the negative lens corrects the aberration, and the positive lens provides focused imaging. The focal length combination of the lenses is complex, which can better correct the aberration, provide better processability and lower cost, fully corrects the aberration of the system and improves the optical resolution of the system.

More importantly, with the transmission and reflection properties of the first optical element and the second optical element, the optical path is effectively folded, which reduces the overall size of the eyepiece optical system, and improves the possibility of subsequent mass production. On the basis of miniaturization, cost and weight reduction for the article, the aberration of the optical system is greatly eliminated, and the basic optical indicators are also improved to ensure high imaging quality and increase the size of the picture angle. Thus an observer can watch large images of full frame, high definition and uniform image quality without any distortion and get visual experience of high liveness via the present invention, and the present article is suitable for head-mounted near-to-eye display devices and similar devices.

In the aforementioned embodiment, the first optical element may be a polarizer with 75% transmission, 25% reflection or 65% transmission, 35% reflection or having a transflective function. The second optical element is only a component with a reflective function, which may be a lens or a metal piece with a reflective function.

As shown in FIG. 1 , a first optical element, a second optical element, and a first lens group arranged along an optical axis direction between a human eye viewing side and a miniature image displayer are included; wherein the optical surface closer to a E side of the human eyes is marked as 1, and so on (2, 3, 4, 5, 6 . . . respectively from left to right), the light emitted from the miniature image displayer is refracted by the first lens group and then reflected on the first optical element to the second optical element, and the light is reflected by the second optical element onto the first optical element, and then transmits to the human eyes through the first optical element.

In a further embodiment, the distance along the optical axis between the first optical element and the second optical element is d₁, the distance along the optical axis between the first optical element and the first lens group is d₂, and d₁ and d₂ satisfy the following relation (5): 0.69<d ₂ /d ₁  (5);

wherein the value of d₂/d₁ may be 0.69, 0.83, 0.88, 0.98, 1.55, 2.37, 3.55, 3.88, 3.99, 4.57, 4.89 and 4.99.

The lower limit of d₂/d₁ in the aforementioned relation (5) is greater than 0.69, which reduces difficulty of correcting an off-axis aberration of the system, and ensures that both a central field-of-view and an edge field-of-view achieve high image quality, so that the image quality in the full frame is uniform.

In a further embodiment, a maximum effective optical caliber of the second optical element is φ₂, which satisfies the following relation (6): φ₂<70 mm  (6);

wherein the value of φ₂ may be 70, 69, 65, 56, 52, 48, 32, 30, 28, 26, 21, etc., and the unit is mm.

In a further embodiment, an effective focal length of the first lens is f₁₁₁, the effective focal length of the first sub-lens group is f₁₁, and f₁₁₁ and f₁₁ satisfy the following relation (7): f ₁₁₁ /f ₁₁<−0.96  (7).

The value of f₁₁₁/f₁₁ may be −0.96, −0.965, −1.32, −1.55, −2.25, −3.57, −5.57, −8.79, −9.91, −10.11, −20.22, etc.

The value of f₁₁₁/f₁₁ in the relation (7) is less than −0.96, which reduces the difficulty of correcting spherical aberration and facilitates the realization of a large optical aperture.

In a further embodiment, the effective focal length f₁ of the first lens group, the effective focal length f₁₁ of the first sub-lens group, the effective focal length f₁₂ of the second sub-lens group and the effective focal length f₁₁₁ of the first lens further satisfy the following relations (8), (9) and (10): 0.67≤f ₁₁ /f ₁≤1.42  (8); −2.64≤f ₁₁₁ /f ₁₁≤−0.97  (9); 0.58≤f ₁₂ /f ₁≤4.54  (10).

The value of f₁₁/f₁ may be 0.67, 0.81, 0.98, 1.235, 1.255, 1.354, 1.367, 1.399, 1.413, 1.42, etc., the value of f₁₁₁/f₁₁ may be −2.64, −2.55, −2.34, −2.22, −2.18, −1.88, −1.68, −1.57, −0.97, etc., and the value of f₁₂/f₁ may be 0.58, 0.963, 1.99, 2.145, 2.548, 3.354, 4.361, 4.54, etc.

By further optimizing the value ranges of the effective focal lengths of the first sub-lens group, the second sub-lens group, the first lens and the system, the optical performance and difficulty of processing and manufacturing of the optical system are better balanced.

In a further embodiment, an included angle of optical axis between the first lens group and second optical element is λ₁, which satisfies the following relation (11): 55°<λ₁<120°  (11);

wherein the value of λ₁ may be 55°, 60°, 66°, 70°, 90°, 100°, 115°, 120°, etc.

In a further embodiment, the second sub-lens group is composed of one lens, the second sub-lens group includes a third lens located between the second lens and the miniature image displayer; the third lens is a positive lens, and an optical surface of the third lens close to the miniature image displayer side is concave to the miniature image displayer;

an effective focal length of third lens is f₁₂₁, which satisfies the following relation (12): 5.83<f ₁₂₁  (12).

The value of f₁₂₁ may be 5.83, 21.2, 21.5, 22, 23.5, 27.8, 30.5, 39.4, 44.5, 57.9, 100.1, etc.

In the aforementioned embodiment, the third lens can better correct the field curvature and astigmatism, which is more conducive to achieving a larger field-of-view angle and higher optical resolution. The optical surface of the third lens close to the miniature image displayer side is concave to the miniature image displayer, which effectively reduces the overall size of the eyepiece optical system, improves the image quality of the system, corrects the distortion, improves the aberrations such as astigmatism and field curvature of the system, and is beneficial for the eyepiece system to realize the high-resolution optical effect of uniform image quality in the full frame.

In a further embodiment, the second optical element includes an optical reflection surface, and the optical reflection surface is concave to the human eyes.

In a further embodiment, the first optical element is a planar transflective optical element, and a reflectivity of the first optical element is Re₁, which satisfies the following relation (13): 20%<Re ₁<80%  (13);

wherein the value of Re₁ may be 20%, 21%, 30%, 47%, 52%, 60%, 65%, 70%, 79%, 80%, etc.

In a further embodiment, an optical surface of second optical element close to the human eye viewing side is a high-reflectivity optical surface, and a reflectivity of the high-reflectivity optical surface is Re₂, which satisfies the following relation (14): 20%<Re ₂  (14);

wherein the value of Re₂ may be 20%, 21%, 30%, 47%, 52%, 60%, 65%, 70%, 80%, 99%, etc.

In one of the embodiments, the eyepiece optical system further includes a planar reflective optical element located between the first lens group and the first optical element; the planar reflective optical element reflects the image light refracted by the first lens group to the first optical element, and the first optical element reflects the image light to the second optical element, and then transmits the image light reflected by the second optical element to the human eyes;

an included angle between the first lens group and the first optical element is λ₂, which satisfies the following relation (16): 60°≤λ₂≤180°  (16);

wherein the value of λ₂ may be 60°, 74°, 80°, 90°, 100°, 130°, 140°, 155°, 167°, 180°, etc.

In a further embodiment, second optical element includes two coaxial optical surfaces of the same face shape.

In a further embodiment, the optical face shape of each lens in first lens group includes an even-order aspherical face shape; and each optical face shape of second optical element is the even-order aspherical face shape.

The aberrations at all levels of the optical system are further optimized and corrected. The optical performance of the eyepiece optical system is further improved.

In a further embodiment, the even-order aspherical face shape satisfies the following relation (15):

$\begin{matrix} {z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{2}r^{2}} + {\alpha_{4}r^{4}} + {\alpha_{6}r^{6}} + {\ldots.}}} & (15) \end{matrix}$

wherein z is a vector height of the optical surface, c is a curvature at an aspherical vertex, k is an aspherical coefficient, α2, 4, 6 . . . are coefficients of various orders, and r is a coordinate of the distance from a point on a curved surface to an optical axis of a lens system.

The aberrations of the optical system (including spherical aberration, coma, distortion, field curvature, astigmatism, chromatic aberration and other higher-order aberrations) are fully corrected, which is beneficial for the eyepiece optical system to further improve the image quality of the central field-of-view and the edge field-of-view, reduce the image quality difference between the central field-of-view and the edge field-of-view, and achieve more uniform image quality and low distortion in the full frame, while realizing a large field-of-view angle and a large aperture.

In a further embodiment, the material of the second optical element is an optical plastic material, such as E48R, EP5000, OKP1, etc.

The aberrations at all levels of the eyepiece optical system are fully corrected, while the manufacturing cost of the optical element and the weight of the optical system are controlled.

The principles, solutions and display results of the aforementioned eyepiece optical system will be further described below through more specific examples.

In the following examples, the diaphragm E may be the exit pupil of imaging for the eyepiece optical system, which is a virtual light exit aperture. When the pupil of the human eyes is at the diaphragm position, the best imaging effect can be observed. The dot array diagram provided in the following examples reflects the geometric structure of the imaging of the optical system, ignores the diffraction effect, is represented by defocused spots formed by a plane section of a focused image of lights with a specified field of view and a specified wavelength, and can contain lights of multiple fields of view and multiple wavelengths simultaneously. Therefore, the imaging quality of the optical system can be directly measured by the density, shape and size of the defocused spots in the dot array diagram, and the chromatic aberration of the optical system can be directly measured by the dislocation degree of the defocused spots at different wavelengths in the dot array diagram. When the RMS (Root Mean Square) radius of the dot array diagram is smaller, the imaging quality of the optical system is higher.

Example 1

The eyepiece design data of Example 1 is shown in Table 1 below:

TABLE 1 Lens Curvature Refrac- Net radius Thickness tive Abbe caliber Cone Surface (mm) (mm) index number (mm) coefficient Dia- Infinity 20 8 phragm 2 Infinity 27 26.65231 3 −36.73472 −19 reflection 46.14225 −8.259855 4 Infinity 0 reflection 25.88797 5 Infinity 27.83279 19.66314 6 −38.05035 6.217359 1.6421  22.406984 9.700683 50.00046 7 4.175037 0.2936443 14.015 −1.785941 8 4.680417 6.322009 1.58913 61.16296  14.31223 −2.128935 9 −18.58306 0.4968615 14.94366 2.224299 10 12.0437 5.228339 1.5928  68.345897 14.31511 11 19.1444 10.44477 12.74182 Image Infinity 44.15212 plane

FIG. 1 is an optical path diagram of the reflective eyepiece optical system of Example 1, including: a first optical element L1 and a second optical element T2 arranged sequentially along the incident direction of the optical axis of the human eyes, and a first lens group T1 located on the optical axis of the miniature image displayer IMG; the first optical element L1 is used for transmitting and reflecting the image light from the miniature image displayer IMG; the second optical element T2 includes an optical reflection surface L2, and the optical reflection surface L2 is concave to the human eye viewing direction; the first optical element L1 reflects the image light refracted by the first lens group T1 onto the second optical element T2, and then transmits the image light reflected by the second optical element T2 to the human eyes EYE.

The effective focal length f_(w) of the eyepiece optical system is −11.54, the effective focal length f₁ of the first lens group T1 is 10.55, the effective focal length f₂ of the second optical element L2 is 22.54, the distance d₁ along the optical axis between the first optical element L1 and the second optical element L2 is 20.0, and the distance d₂ along the optical axis between the first optical element L1 and the first lens group T1 is 33.05, wherein the first lens group T1 includes the first sub-lens group T11 and the second sub-lens group T12. The effective focal lengths f₁₁ and f₁₂ of the two sub-lens groups are 14.61 and 42.99, respectively. The first sub-lens group T11 is a positive lens group, the first lens T111 is a negative lens with an effective focal length f₁₁₁ of −14.18, and the second lens T112 is a positive lens. The second sub-lens group T12 includes a third lens T121. Then f₁/f_(w) is −0.91, f₂/f_(w) is −1.95, f₁₁/f₁ is 1.38, f₁₁₁/f₁₁ is −0.97, f₁₂/f₁ is 4.07, f₁₂₁ is 42.99, d₂/d₁ is 1.65, and λ₁ is 66°.

FIGS. 2, 3 a, 3 b and 4 are respectively a dot array diagram, a field curvature diagram, a distortion diagram and a transfer function MTF curve graph, which reflect that the lights of respective view fields in this example has high resolution and small optical distortion in the unit pixel of the image plane (the miniature image displayer IMG), the resolution per 10 mm per unit period reaches more than 0.8, the aberration of the optical system and the image drift are well corrected, and a display image of uniformity and high optical performance can be observed through the eyepiece optical system.

Example 2

The eyepiece design data of Example 2 is shown in Table 2 below:

TABLE 2 Lens Curvature Refrac- Net radius Thickness tive Abbe caliber Cone Surface (mm) (mm) index number (mm) coefficient Dia- Infinity 20 4 phragm 2 Infinity 27 20.91639 3 −40.32301 −19 reflection 35.71806 −9.951578 4 Infinity 0 reflection 45.61296 5 Infinity 18.08284 10.04825 6 −19.52309 7.217886 1.63191 23.416119 7.032871 20.31158 7 5.904725 0.6343975 12.63061 −1.777835 8 6.000741 4.65972 1.69384 53.151009 13.93238 −1.358971 9 −9.417197 0.1636894 14.4235 −0.2500272 10 8.686751 3.498207 1.58912 61.245793 12.98211 11 14.44506 7.930628 11.50216 Image Infinity 6.037721 plane

FIG. 5 is an optical path diagram of the reflective eyepiece optical system of Example 2, including: a first optical element L1 and a second optical element T2 arranged sequentially along the incident direction of the optical axis of the human eyes, and a first lens group T1 located on the optical axis of the miniature image displayer IMG; the first optical element L1 is used for transmitting and reflecting the image light from the miniature image displayer IMG; the second optical element T2 includes an optical reflection surface L2, and the optical reflection surface L2 is concave to the human eye viewing direction; the first optical element L1 reflects the image light refracted by the first lens group T1 onto the second optical element T2, and then transmits the image light reflected by the second optical element T2 to the human eyes EYE.

The effective focal length f_(w) of the eyepiece optical system is −9.29, the effective focal length f₁ of the first lens group T1 is 7.64, the effective focal length f₂ of the second optical element L2 is 20, the distance d₁ along the optical axis between the first optical element L1 and the second optical element is 19, and the distance d₂ along the optical axis between the first optical element L1 and the first lens group T1 is 25.3, wherein the first lens group T1 includes the first sub-lens group T11 and the second sub-lens group T12. The effective focal lengths f₁₁ and f₁₂ of the two sub-lens groups are 10.86 and 30.19 respectively, the first sub-lens group T11 is a positive lens group, and the first lens T111 is a negative lens with an effective focal length f₁₁₁ of −28.66. The second lens T112 is a positive lens. The second sub-lens group T12 includes a third lens T121. Then f₁/f_(w) is −0.82, f₂/f_(w) is −2.15, f₁₁/f₁ is 1.42, f₁₁₁/f₁₁ is −2.64, f₁₂/f₁ is 3.95, f₁₂₁ is 30.19, d₂/d₁ is 1.33, and λ₁ is 79°.

FIGS. 6, 7 a, 7 b and 8 are respectively a dot array diagram, a field curvature diagram, a distortion diagram and a transfer function MTF curve graph, which reflect that the lights of respective view fields in this example has high resolution and small optical distortion in the unit pixel of the image plane (the miniature image displayer IMG), the resolution per 10 mm per unit period reaches more than 0.8, the aberration of the optical system and the image drift are well corrected, and a display image of uniformity and high optical performance can be observed through the eyepiece optical system.

Example 3

The eyepiece design data of Example 3 is shown in Table 3 below:

TABLE 3 Lens Curvature Refrac- Net radius Thickness tive Abbe caliber Cone Surface (mm) (mm) index number (mm) coefficient Dia- Infinity 41 4 phragm 2 −30.67427 −17 reflection 31.16804 −6.010179 3 Infinity 17 reflection 13.05963 4 −21.11542 4.203534 1.64219 22.406984 6.579412 27.80151 5 4.622147 −0.00189 10.41055 −1.4851 6 4.622147 3.891791 1.6691  55.4023  10.4043 −1.485114 7 −12.73079 9.429228 10.92041 1.638756 8 12.44054 2.167581 1.5928  68.345897 12.21502 9 16.01564 9.456845 11.64446 Image Infinity 10.876 plane

FIG. 9 is an optical path diagram of the reflective eyepiece optical system of Example 3, including: a first optical element L1 and a second optical element T2 arranged sequentially along the incident direction of the optical axis of the human eyes, and a first lens group T1 located on the optical axis of the miniature image displayer IMG; the first optical element L1 is used for transmitting and reflecting the image light from the miniature image displayer IMG; the second optical element T2 includes an optical reflection surface L2, and the optical reflection surface L2 is concave to the human eye viewing direction; the first optical element L1 reflects the image light refracted by the first lens group T1 onto the second optical element T2, and then transmits the image light reflected by the second optical element T2 to the human eyes EYE.

The effective focal length f_(w) of the eyepiece optical system is −14.91, the effective focal length f₁ of the first lens group T1 is 16.95, the effective focal length f₂ of the second optical element L2 is 10.57, the distance d₁ along the optical axis between the first optical element L1 and the second optical element L2 is 20.99, and the distance d₂ along the optical axis between the first optical element L1 and the first lens group T1 is 17.3, wherein the first lens group T1 includes the first sub-lens group T11 and the second sub-lens group T12. The effective focal lengths f₁₁ and f₁₂ of the two sub-lens groups are 11.33 and 76.7 respectively, the first sub-lens group T11 is a positive lens group, and the first lens T111 is a negative lens with an effective focal length f₁₁₁ of −12.76. The second lens T112 is a positive lens. The second sub-lens group T12 includes a third lens T121. Then f₁/f_(w) is −1.14, f₂/f_(w) is −0.71, f₁₁/f₁ is 0.67, f₁₁₁/f₁₁ is −1.13, f₁₂/f₁ is 4.53, f₁₂₁ is 76.7, d₂/d₁ is 0.82, and λ₁ is 80°.

FIGS. 10, 11 a, 11 b and 12 are respectively a dot array diagram, a field curvature diagram, a distortion diagram and a transfer function MTF curve graph, which reflect that the lights of respective view fields in this example has high resolution and small optical distortion in the unit pixel of the image plane (the miniature image displayer IMG), the resolution per 10 mm per unit period reaches more than 0.9, the aberration of the optical system and the image drift are well corrected, and a display image of uniformity and high optical performance can be observed through the eyepiece optical system.

Example 4

The eyepiece design data of Example 4 is shown in Table 4 below:

TABLE 4 Lens Curvature Refrac- Net radius Thickness tive Abbe caliber Cone Surface (mm) (mm) index number (mm) coefficient Dia- Infinity 37 6 phragm 2 24.75482 −15 reflection 18.62021 −0.6579222 3 Infinity 14.99967 reflection 12.51195 4 −20.92172 7.297555 1.639081 23.28987  5.821106 27.88114 5 4.010729 0.2559976 5.748953 −1.742569 6 4.635192 2.632533 1.6779  54.896588 5.833988 −1.991904 7 −8.122444 3.409442 5.949331 −0.1787041 8 11.03583 7.869539 1.6516  58.416296 6.548139 9 15.03463 7.25431 5.512029 Image Infinity 5.630769 plane

FIG. 13 is an optical path diagram of the reflective eyepiece optical system of Example 4, including: a first optical element L1 and a second optical element T2 arranged sequentially along the incident direction of the optical axis of the human eyes, and a first lens group T1 located on the optical axis of the miniature image displayer IMG; the first optical element L1 is used for transmitting and reflecting the image light from the miniature image displayer IMG; the second optical element T2 includes an optical reflection surface L2, and the optical reflection surface L2 is concave to the human eye viewing direction; the first optical element L1 reflects the image light refracted by the first lens group T1 onto the second optical element T2, and then transmits the image light reflected by the second optical element T2 to the human eyes EYE.

The effective focal length f_(w) of the eyepiece optical system is −15.94, the effective focal length f₁ of the first lens group T1 is 8.1, the effective focal length f₂ of the second optical element L2 is 18, the distance d₁ along the optical axis between the first optical element L1 and the second optical element L2 is 15, and the distance d₂ along the optical axis between the first optical element L1 and the first lens group T1 is 15, wherein the first lens group T1 includes the first sub-lens group T11 and the second sub-lens group T12. The effective focal lengths f₁₁ and f₁₂ of the two sub-lens groups are 11.3 and 4.68 respectively, the first sub-lens group T11 is a positive lens group, and the first lens T111 is a negative lens with an effective focal length f₁₁₁ of −12.53. The second lens T112 is a positive lens. The second sub-lens group T12 includes a third lens T121. Then f₁/f_(w) is −0.51, f₂/f_(w) is −1.13, f₁₁/f₁ is 1.40, f₁₁₁/f₁₁ is −1.11, f₁₂/f₁ is 0.58, f₁₂₁ is 5.84, d₂/d₁ is 1, and λ1 is 56°.

FIGS. 14, 15 a, 15 b and 16 are respectively a dot array diagram, a field curvature diagram, a distortion diagram and a transfer function MTF curve graph, which reflect that the lights of respective view fields in this example has high resolution and small optical distortion in the unit pixel of the image plane (the miniature image displayer IMG), the resolution per 10 mm per unit period reaches more than 0.9, the aberration of the optical system and the image drift are well corrected, and a display image of uniformity and high optical performance can be observed through the eyepiece optical system.

All the data of the aforementioned Examples 1 to 4 meet the parameter requirements recorded in the Summary, and the results are shown in Table 5 below:

TABLE 5 f₁/f_(w) f₂/f_(w) f₁₁/f₁ f₁₁₁/f₁₁ f₁₂/f₁ Example 1 −0.91 −1.95 1.38 −0.97 4.07 Example 2 −0.82 −2.15 1.42 −2.64 3.95 Example 3 −1.14 −0.71 0.67 −1.13 4.53 Example 4 −0.51 −1.13 1.4  −1.11 0.58

The present application provides a head-mounted near-to-eye display device, including a miniature image displayer, and further including the reflective eyepiece optical system according to any one of the foregoing content; and the eyepiece optical system is located between the human eyes and the miniature image displayer.

Preferably, the miniature image displayer is an organic electroluminescent device.

Preferably, the head-mounted near-to-eye display device includes two identical reflective eyepiece optical systems.

To sum up, respective lenses in the first lens group of the reflective eyepiece optical system of the aforementioned examples of the present invention adopt a focal length combination of negative, positive and positive, which fully corrects the aberration of the system and improves the optical resolution of the system. More importantly, with the transmission and reflection properties of the first optical element and the second optical element, the optical path is effectively folded, which reduces the overall size of the eyepiece optical system, and improves the possibility of subsequent mass production. On the basis of miniaturization, cost and weight reduction for the article, the aberration of the optical system is greatly eliminated, and the basic optical indicators are also improved to ensure high imaging quality and increase the size of the picture angle. Thus an observer can watch large images of full frame, high definition and uniform image quality without any distortion and get visual experience of high liveness via the present invention, and the present article is suitable for head-mounted near-to-eye display devices and similar devices.

It should be understood that improvements or changes can be made by those of ordinary skills in the art according to the aforementioned description, and all these improvements and changes should fall within the claimed scope of the appended claims of the present invention. 

What is claimed is:
 1. A reflective eyepiece optical system, which is composed of a first optical element and a second optical element which are arranged sequentially along an incident direction of an optical axis of human eyes, and a first lens group located on an optical axis of a miniature image displayer; wherein the first optical element is used for transmitting and reflecting an image light from the miniature image displayer; the second optical element comprises an optical reflection surface, and the optical reflection surface is concave to the human eyes; the first optical element reflects the image light refracted by the first lens group to the second optical element, and then transmits the image light reflected by the second optical element to the human eyes; an effective focal length of the eyepiece optical system is f_(w), an effective focal length of the first lens group is f₁, an effective focal length of the second optical element is f₂, and f_(w), f₁, and f₂ satisfy the following relations (1) and (2): f ₁ /f _(w)<−0.50  (1); f ₂ /f _(w)<−0.70  (2); the first lens group is composed of a first sub-lens group and a second sub-lens group arranged sequentially along an optical axis direction from a human eye viewing side to a miniature image displayer side; an effective focal length of the first sub-lens group is f₁₁, which is a positive value; an effective focal length of the second sub-lens group is f₁₂, which is a positive value; and f₁₁, f₁₂ and f₁ satisfy the following relations (3) and (4): 0.66<f ₁₁ /f ₁  (3); 0.57<f ₁₂ /f ₁  (4); the first sub-lens group is composed of two lenses which are a first lens away from the miniature image displayer side and a second lens close to the miniature image displayer side respectively; the first lens is a negative lens; the second lens is a positive lens; and the second sub-lens group is composed of a third lens located between the second lens and the miniature image displayer, and the third lens is a positive lens.
 2. The reflective eyepiece optical system according to claim 1, wherein the distance along the optical axis between the optical surface of the first optical element away from the side of the human eyes and the optical reflection surface in the second optical element is d₁, the distance along the optical axis between the optical surface of the first optical element away from the human eye viewing side and the optical surface in the first lens group closest to the human eye viewing side is d₂, and d₁ and d₂ satisfy the following relation (5): 0.69<d ₂ /d ₁  (5).
 3. The reflective eyepiece optical system according to claim 1, wherein a maximum effective optical caliber of the second optical element is φ₂, which satisfies the following relation (6): φ₂<70 mm  (6).
 4. The reflective eyepiece optical system according to claim 1, wherein an effective focal length of the first lens is f₁₁₁, the effective focal length of the first sub-lens group is f₁₁, and f₁₁₁ and f₁₁ satisfy the following relation (7): f ₁₁₁ /f ₁₁<−0.96  (7).
 5. The reflective eyepiece optical system according to claim 1, wherein the effective focal length f₁ of the first lens group, the effective focal length f₁₁ of the first sub-lens group, the effective focal length f₁₂ of the second sub-lens group and the effective focal length f₁₁₁ of the first lens further satisfy the following relations (8), (9) and (10): 0.67≤f ₁₁ /f ₁≤1.42  (8); −2.64≤f ₁₁₁ /f ₁₁≤−0.97  (9); 0.58≤f ₁₂ /f ₁≤4.54  (10).
 6. The reflective eyepiece optical system according to claim 1, wherein an included angle of the optical axis between the first lens group and the second optical element is λ₁, which satisfies the following relation (11): 55°<λ₁<120°  (11).
 7. The reflective eyepiece optical system according to claim 1, wherein an optical surface of the third lens close to the miniature image displayer side is concave to the miniature image displayer; and an effective focal length of the third lens is f₁₂₁, which satisfies the following relation (12): 5.83<f ₁₂₁  (12).
 8. The reflective eyepiece optical system according to claim 1, wherein the first optical element is a planar transflective optical element, and a reflectivity of the first optical element is Re₁, which satisfies the following relation (13): 20%<Re ₁<80%  (13).
 9. The reflective eyepiece optical system according to claim 1, wherein an optical surface of the second optical element close to the human eye viewing side is a high-reflectivity optical surface, and a reflectivity of the high-reflectivity optical surface is Re₂, which satisfies the following relation (14): 20%<Re ₂  (14).
 10. The reflective eyepiece optical system according to claim 1, wherein the second optical element comprises two coaxial optical surfaces of the same face shape.
 11. The reflective eyepiece optical system according to claim 1, wherein the optical face shape of each lens in the first lens group comprises an even-order aspherical face shape; and each optical face shape of the second optical element is the even-order aspherical face shape.
 12. The reflective eyepiece optical system according to claim 11, wherein the even-order aspherical face shape satisfies the following relation (15): $\begin{matrix} {{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{2}r^{2}} + {\alpha_{4}r^{4}} + {\alpha_{6}r^{6}} + \ldots}};} & (15) \end{matrix}$ wherein z is a vector height of the optical surface, c is a curvature at an aspherical vertex, k is an aspherical coefficient, α2, 4, 6 . . . are coefficients of various orders, and r is a coordinate of the distance from a point on a curved surface to an optical axis of a lens system.
 13. The reflective eyepiece optical system according to claim 1, wherein the material of the second optical element is an optical plastic material.
 14. A head-mounted near-to-eye display device, comprising a miniature image displayer, wherein it further comprises the reflective eyepiece optical system according to claim 1; and the eyepiece optical system is located between human eyes and the miniature image displayer.
 15. The head-mounted near-to-eye display device according to claim 14, wherein the miniature image displayer is an organic electroluminescent device.
 16. The head-mounted near-to-eye display device according to claim 14, wherein the head-mounted near-to-eye display device comprises two identical reflective eyepiece optical systems. 